Purification of valuable hydrocarbons



Patented Feb. 4, 1941 UNITED STATES T QFFICE PURIFICATION OF VALUABLE vnYnnocAnBoNs Frank J. Soday, Upper Darby, Pa., assignor to Q United GasImprovement Company, a corpora- [tion of Pennsylvania No Drawing. pplication May-26, 1938,

' Serial No. 210,170

'7 Claims.

This invention pertains generally to the purification of hydrocarbons,and pertains particularly to the purification of resin-formingunsaturated hydrocarbons obtained from (1) gas con- 6 densates and taroils produced in the manufacture of artificial gas; (2) crackedpetroleum products; (3) coal tar distillates; and (4) synthetic sourcessuch as processes for'the manufacture of synthetic styrene.

l The invention pertains more particularly to 2o quantities of otherreadily condensible materials.

The latter condensates as well as thedistillate from the tar areknown'generally as light oil and are sources for many resin-formingunsaturated hydrocarbons such as indene, styrene, methyl 25 styrene,cyclopentadiene, isobutylene, isoprene,

piperylene, butadlene, etc. 1

With ordinary methods of fractional distillation as now practiced, it isimpossible to separate the resin-forming unsaturated hydrocarbons in 30a substantially pure state because of the presence of other materialswhich apparently are either of similar boiling point ,or are capable offorming azeotropic'mixtures with the desired hydrocarbon. Furthermore,many of these materials are. 35 polymerizable with heat which adds todistillation difficulties. a

For instance a typical styrene fraction obtained by ordinarydistillation processes will contain hardly more than 50% styrene, and atypical- 4 indene fraction will contain hardly more than 80% indene. i

Such fractions as well as those of lower and higher. concentration aregenerally suitable for the manufacture of synthetic resins, by polymeri-45 .zation. except that the resulting resins are very often too inferiorwith respect to color, color stability, electrical resistance, moldingproperties, freedom from crazing, thermal stability, melting point,specific viscosity, molecular weight and to mechanical strength as to beof any considerable value. I

I find that these deficiencies are generally traceable to the presenceduring the polymerization of certain contaminating materials. 65 While Ihave not asyet exactly determined the character of these impurities,experimental evidence indicates that they maybe classified in certainspeclficgroups; 1

For example, a typicalstyrene fraction obtained from light oil wasanalyzed and "found to con- ,5 tain approximately 0.1% sulfur. Thisindicates that crude styrene fractionsobtained from the above sourcescontain a relatively large quantity of sulfur containing materials suchas mercaptans, disulfides, or derivatives of thiophene and relatedcompounds. j

Another portionwas treated with a mercuratting solution which resultedinthe production of a copious precipitate, 'Precipitates obtained withdifferent portions of the starting material varied in color from afaintyellow to -a light brown.

This indicates,,among other things, the presence of superaromaticcompounds such-as substituted thiophene and thiophene 1homologues.

The treatment of various light oil fractions with ammoniacal cuprouschloride'resulted in the formation of a heavy yellow precipitate. Thisindicates the presence ofeacetylenic compounds such as phenyl acetylene.

Similar tests made, with) pure styrene iluted with xylene to.the'samerconcentration as the crude styrene iractions treated above gaveresults which werenegative in each ,case.

Other types ofimpurities are doubtless present also, although specifictests'havenot as yet been devisedfor their detection Among these typesof impurities may be included oxygenated compounds, organic peroxidesand oxides, organic peracids, aldehydes; amines; [and other reactiveclasses of compounds.

As indicated above it is difii'cult, if not impossible, to prepare acommercial grade of resin, such as polystryene, from.crudeliglitoilfractions unless at least some o'ffthe contaminatingimpurities 40 are removed. f

While the exact influence of'these contaminating materials isnotknownitmay be pointed out that they may act (1) as acceleratorsresulting in the production of polystryene of relatively poor qualityunder polymerizing conditions which would'nor'mally result in theproduction of a good grade of polystryene; (2) as. inhibitors reducingthequantity of polystyrenepbtained under normal. polymerizing"conditions, and/or (3) they may take part inthe reaction and become anin tegralpart of the resin; molecule.

The presence of contaminating. impurities in the polymer molecule wouldundoubtedly weaken it, causing the resin to be less stable to heat andto readily decompose with the formation of nude-- sired color bodies.

lates in the manufacture of motor fuels removes most, if not all, of anystyrene present.

It seems probable that any material which is sufllclently reactive to becapable of useifor the purification of the crude r e sin-formingunsaturated hydrocarbons will also react with thennl Petroleumtechnologists. have made many at- I tempts to utilize mixtures ofsulfuric acid and 2 residues.

potassium permanganate for. "refining lightoil distillates. Suchattemptshave been unsuccessful, since the potassium permanganate invariablycaused the distillate to become darker in color.

I have found,ahowever, that,zby a .proper choice of conditions such:astemperature, time of contact, method of applicationand so forth, thevarious reactions maybe controlled with the result that practicallyallofthe undesired contaminating materials, including color and.color-formingcompounds, maybe removed without a considerable ioss of the desiredhydrocarbon. I

- Thefollowing example will serve toillustrate the invention:- t

A 500 cubic centimeter (440.5 grams) sample of a typical crudestyrenecut obtained from the fractionation of light "oil and. containing 33.3

grams of styrene per 100'cubic centimeters was agitated for 10 minuteswith 25 'cubic centimeters of a 70% solution of sulfuric-acid containing0.125

gram of mum at a tem'peratureof 20 C. The mixture was then allowed tostandfor 3 minutes during which time-a sludge settled out andwasremoved. An additional .25jcubic centimeters 'of the foregoing reagentwas then added and the mixture again agitated "for-10minutes. -Asettling'time of 5- minutes followed during which sludge wasintermittently removed- The sample was thenItreated-with 25' cubiccentimeters of a 20% aqueoussolution ofsodium hydroxide with moderatestirring. .After permitting the materials to settle theaqueous layer wasremoved.

The sample was nowewashed ten successive times with -20'cu biccentimeters ofrwater. The last washings were neutral-to litmus whichindicated complete removal .of. acid and; alkaline The totaltreatinglossup to thispoint was only 1.1% by weightof the starting material. I

The refined sample of crude styrene was now dried over anhydroussodiumsulfate.

The drying loss was, 2.2% by weight of the starting material. Altho,ug hthisv loss is not excessive, I wish to point out that "most of it} wasdue almost entirely to, mechanical absorption by the drying agent and.that the lost material might be reclaimedbywashing thefanhydrous sodiumsulfatewlthasuitable solvent; I

The dried' material was then f distilled under. vacuum usinga *1pressure ,of 40 millimeters absolute. i j L This occasioned an'additional loss of 3.7% of the original chargenf I jI j The crudestyrene' wasnow ready for polymerization.

2,230,274 t. I I

It is to be noted that despite the reactive nature in large scaleoperations, I a [I color on the spectively on the Gardner color scale."

of the material being treated the total treating loss was only 7.3% byweight of the starting material, or 10.7% by weight of thestyrenecontainedf Most of these losses in thcstarting material. were ofa mechanical nature and are, therefore,

susceptible to considerable reduction,zparticularly I The refinedstyrene solution had a well known Gardner color scale of 0.00 (waterstarting material. I I

A sample of the refinedfstyrene solution was white) as compared to acolor of 2.5 shown by the subjected to polymerization for 4 days at atemperature of 145 C. in a nitrogen atmosphere.

The resin yield was 32.0 grams per 100 cubic centimeters of refinedsolution. The starting material itself contained only 33.3 grams ofstyreneper 100 cubic centimeters officrude soluf 20 Another sample ofthe refined styrene solution tion.

and a sample of the starting. material were each subjected to identicalpolymerizing conditions; namely heating'for a-l0 day period at 100 C. inan atmosphere of nitrogen."

scale.

. v '25 The resin obtained from .the refined materialhad a color of 1.0ontheGardner color scale.

, whereas the resin obtained from the unrefined A sample of each portionof resin was subjected to molding at a temperature-of..200-C. and apressure of 2000 pounds per square inch. The

molded refined materialhad a color of .0.9.on

the Gardner'color scale,. whereas the molded un--' refined mat iaada'color of 2.4.on .the Gardner color scale. I V 7 Furthermore,therefined resin possesses unusual color stability as shown byv thefollowing I test.

I A sample of resin obtained from the refined material and asampleofresin obtained from heated for 2 days in an atmosphere'of nitrogen andan atthe unrefined material-were each mosphere of air at a temperatureof 145 C.

At the end of this rather severe treatment-the refined resin had a'colorof6.0and 8.0 respectively on the Gardner color scale; whereas the Iunrefined resin had a-color of 12.0 and 12.5 re- -The melting pointandspecific viscosity of the refined resin was 181LC. and 0.3029respectively, whereas the melting point and specific viscosity of theunrefinedre'sin was 154 (hand 0.2275 5 respectively. I

Tests also show that the refined. resin possesses a much bettermechanical strength and istougher than the unrefined resin, thatitsIm'olding'proper- 'ties' are considerably improved and that it ismore uniform in texture and appearance. While solutions of sulfuricacidof any desired strength may be employ d. v,I prefer to use sulfuricacid of at least s'trengthfandup to say 90%;strength. Acid of'high'er orlower strength' may be employed. For instanceyacid of lower strength maybe used for-purifying solutions of olefines and diolefinesofhigherconcentration. Acid of higher strength is preferably free ofuncombinedsulfur dioxide 'or sulfur trioxide.

I n a that solutions of sulfuric acid of to 5 80% concentration are verysatisfactory, and that 'a' solution of concentration isexcellent for allaround purposes I I II v I The acid solution should preferably containat "least 0.1% of spoon-n potassium permanganate or the manganeseionequivalent of a similar compound of manganese, for-instance, sodiumpermanganate. However, broadly speaking, anycompound capable. offurnishing an nese mightbe used. o g I From 1% to% of permanganate-by;weight ion containing mangawill: meet most conditions.

High concentrations lend themselves to conditions requiring moredrastic.v treatment. As an,

example the, proportion of :permanganatemay be as high as 50%. by weightor higher I Although any suitable proportion of acids'olution may beemployed,.I prefer to'use from-0.2% to 50% by volume based upon thematerial being treated. I 1

I find that from 2% to of acid solution by volume of the material undertreatment gives very satisfactory. results.

If desired, suitable other additions may be made to theacid solution. g

Examples of materials whichmight be ,added to the acid solutioncontaining. the manganese ion are (1) retarding agents, which have fortheir specific purpose the reduction of the effect of; the acid upon theolefines, dioleiines, and aromatic hydrocarbons present in ,thefraction,such as boric acid and other compounds of ,boron:. (2) other oxidizingagents such as KzCnO'r,-;KCrO4, NaaCrn01,NaCrO4, chromic acid, ferricoxide,lead oxide, and the like; and (3) inhibitors, thefunction of whichis to, inhibit thepolymerization of the unsaturated hydrocarbons duringthe treating process, such as p-tertlary butyl catechol-,-.;;- -4diaminophenol dihydrochloride, 2-amino-5Qhydroxytoluene, p-benzylaminophenol, and pmethyl aminophenol sulfate. Q Both (1) and (2) may beadded if desired; Y- Acid mixtures containing the manganese ion of whichsulfuric acid is one of the constituentsmay be used with excellentresults. Examples 'offacids which maybe mixed with the sulfuricacid'solution are acids' or acid anhydridescontaining phosphorus such asany of the phosphoric ac'ids, any of the phosphorous-acids, P205 andP203,

acetic acid, and sulfonic acids, such as benzene sulfonic acid, toluenesulfonlc acid,- xylene "sulfonic acid, ethyl benzene sulfonic acid, etc.

While any suitable'temperature maybe employed during the varioustreating steps, Iprefer "to maintain the temperature between 540 C.

and 75 0.

' Temperatures between approximately -109 C. and 30 C. are verysatisfactory.

However, in general the temperature should 7 decrease with increase'inconcentration of sulfuric acid to avoid discolorization of the finishedmaterial due to thereagent. Therefore", inj any case the temperatureshould be sufficiently'flow to avoid such discoloration.

Unless certain precautions are observed, the

addition of the neutralizing agentto th'e acid washed material mayresultin the formationof an emulsion.

I, therefore. prefer to add the neutralizingsolution slowly and withmoderateagitation', although. alternate procedures may be employed.

Such alternate procedures include (a) the removal of the acid additionproducts byvarious solvents such as alcohol or glycerol before the'aikali'wash; (b) the addition of certain materials to the alkali washsuch as liquid rosin, petroleum carboxylicacids, ethyl alcohol,oleic..acid,"and naphthenic acids; and (c) the addition of varisludgepresent. ally serves to completely remove all of the water during thetreating process.

ous emulsion inhibiting agents to the alkali was such asaldehydes. v

I However, emulsions if formed can generally be broken by the additionof an absorbent material "suchas fullers earth followedby filtering, orby the useof other suitable methods, such as electrical precipitation,the addition of various, in-

"organic salts to the emulsion, and the like.

Any other suitable neutralizing agent may be employed for'the removal ofexcess acid and acid residues from the material under treatment.Examples of such neutralizing agents are lime. NazCO KOH, ammonia,fullers earth, clay. and activated carbon.

These neutralizing agents may be applied in the solid form, or in theform of solutions in water or other solvents. They may be used alone, orin combination with one or more other neutralizing agents, in which casevthey may be added to the treated solution together, or successively.For example, the acid-treated solution canbe treated with clay to removethe major portion of the acid and sludgepresent, the clay and adsorbedmaterials removed by filtration or by other suitable means, and solidNazCoa added to the;solution to, remove any residual acid orIncidentally, this treatment usupresent in the treated solution,rendering unnecessaryany further drying operations.

o If desired, inert solvents such as petroleum naphtha and carbontetrachloride may be added to the material under treatment either beforeor Such materials are usually added to reduce the loss of olefines anddiolefines present, although they may have other functions. I

The crude fractions which maybe treated by gmyprocess may have anyreasonable boiling range.

' For-instance, crude styrene fractions may have i a boiling range offrom 125 C. to 165 C. or

H wider, although, I prefer to use crude styrene fractions with boilingranges which do not greatly -.exceed,140 C, to 150 C.

Excellent results are obtained when usingcrude styrene fractionswithboiling ranges not exceeding 142 C. to 148 C.

What has just been said with respect to the boiling ranges of crudestyrene fractions applies mcomparably to fractions of other unsaturatedhydrocarbons.

For instance, a. valuable methyl styrene fraction composed largely ofpara-methyl and metamethyl styrenes is obtained from light oil whenapproximately 80% to 95% boils between 167 C.

. and 175 0. Likewise, a valuable indene fraction is obtained from lightoil when approximately 80% to 95% boils between 177 C. and 186 C.-

In' general, and with all other conditions unchanged, the extent ofpurification will, generally .speaking, bedirectly proportional to thenarrowness in boiling range of the starting material.

Results comparable to those particularly set forth above in connectionwith styrene are obfractions.

may then be. contacted with additional quantities 'lilso as an example,a purified indene'fractlon may be polymerized by adding it too.suspensionof 2.0% by weight of ferric chloride in toluene,

followed by stirring for a period of three hours. The catalyst isthenhydrolyzed by the addition of the theoretical amount of sodiumhydroxide in the form of a 20% solution. The mixture then is filteredand the unpolymerized material-removed by steam distillation. "Thepolymerized material has a color of 4.0m the Gardner color scale.

Unwashed indene polymerized in a similar manner has a color of 8.0 onthe Gardner color scale. A'crude styrene solution containing anyquantityofstyrene such as from 1.0% to 99% maybe refined by my method.

Excellent results are obtained with styrene solutions containing from10% to 80% styrene.

Comparable ooncentrationsapply to the other unsaturated hydrocarbons tobe refined by my method.

1 'Further examples of such other unsaturated hydrocarbons are the otherolefines and diole'fines obtained from light oil, from drip oil (fromgas the'large number of processes and apparatus for leaching generally,for bringing mineral oil into contact with a chemical reagent, for thesolvent extraction of mineral oils, etc. which may be adapted forcarrying out the invention. 1 1

In certain cases it may be advisable totreat the unsaturatedhydrocarbon, or fractions containing the unsaturated hydrocarbons, withsuccessive portions of the acid solution in order to effect a morethorough purification of the hydrocarbon solution, or a more economicalutilization of the acid mixture,'or both. The batchwise addition of theacid mixture may be made with or without the removal of a portion'or allof the acid and acid sludge from the preceding application. and with orwithout additional refining steps, such as neutralization, drying,fractionation, and/or crystallization between successive batchwiseadditions ofthe acid refining agent. 7

In certain cases it may be found to be desirable to contact freshcharges of the unsaturated hydrocarbon fractions with spent acidsolution? and/or'acid sludge and-residues from the pre-i ceding refiningstep in. order tosecure greater economy in the use of the acid solutionand/or 9.; more thorough purification of the hydrocarbon.

The hydrocarbon fraction so treated of fresh acid solution, either withor without pre-i viously removing the acid sludge from the initialtreatment and with or without additional refining steps, such asneutralization, drying, fractiona tion and/or distillation, and therefining opera-.- tion completed-in the normal manner, namely by 1separation of the respective layers, followed by neutralizing, drying,and/or distilling.

The treated material, of course, lendsitself to further purification,should this be desired.

jSuchfurther purification'may' be by contactwith clay,= -with activatedcarbon, or with diatomaceous earthat-anysuitable.temperaturejorbydistilla tion at anydesired pressure,=or by, partial poly-3'; merizauonfollowed byremovalof undesirable-f constituents, or by'fractionalcrystallizatio'rhorb other physical or chemical means By operating myprocess; more drastically" it maybe employed'to completely remove theolefins and' diolefines "present in the material undergoing treatmentleaving. the 'arOmaticJhydrocarbons, Special solvents-maybe prepared inthis manner. I l v naphthenes and/or paraflins unchanged.

'- Other variations will become-apparent "to pen-- I sons skilled in theart upon becoming familiar with this invention.

The treating process as outlined in thee'x'ample listed may be greatlysimplified in most cases. For example, I find that styrene solutions maybe refined in a satisfactory m'anner by treatment with the acidsolution, followed'by the application of-clay or activated carbon,either alone or'in conjunction with'other neutralizing agents, suchassodium carbonate or'lime, and the removal of all-g. some material'fromthe treated solution by filtration or by other; suitable means.treatment is usually necessary.

Whilefthe invention has been more particustituents maybe substituted ofwhich'sodium permanganate and manganeseiidioxide are ex!- amp'lesi "Ingeneral, any compoundcapable of yieldingan ion containing manganese whenadded to the acid might-be. added to or substitutedj'forKMnOa, q

Bytthe-xterm ion containingymanganese! as "used in? the specificationand in the claims I mean 7 manganic ion, manganous ion, permanganateion;

and/or in general any ion containing manganese.

.The;term-- perm-anent color as, usedin the .claims; is. intended tomean color which remains after ,the removal of acid and acid reactionprod-1;

uctssuch as by neutralization and water washing" followed bydistillation.

; larly-{described in connection with the addition;

of potassium permanganate to sulfuricacid /it" istob'e understood thatother compounds com "tainingzmang'anese and oxygen as essential ,con-

It.i,s,-theref ore, tobe understood'that the above,

examples are by way of illustration and that a changes; fomis'sions,additions,v ,fsubstitutions,

scope of'the claims withoutdepartin g frornfthe spirit of the inventionwhich is intended to be limited only as required by the prior art. I

I,claim:

and/o'rmodifications might 'be madewithin the in concentrationbut freefrom any appreciable 'uncombinedg sulfur dioxide and'sulfur' trioxideand'containing a compound capable of-ifur'nishingan ion containingmanganese in quantity equivalent to atleast 0.1% by weightofpot-assiumpermanganate,-said contact o'fisaid frac-;

tion and's'aid reagent taking place ata temperature below 75 0. andunder conditions including acid concentration and temperaturesuificiently drastic to remove color forming bodies 'but insufiicientlydrastic to polymerizeia large part of said resin-forming unsaturatedhydrocar- 1 b-on content and insufliciently drastic to add anyappreciable permanent color to said fraction; andQ removingsaid reagentfrom said fraction. "1

least 50% in concentration and containing a compound capable offurnishing manganese ion in quantity equivalent to at least 0.1% byweight of potassium permanganate, said treatment taking place at atemperature below 75 C. and under conditions including acidconcentration and temperature sufliciently drastic to remove colorforming bodies but insufficiently drastic to polymerize a large part ofsaid resin-forming unsaturated hydrocarbon and insufiiciently drastic toadd any appreciable permanent color to said cut, and removing saidreagent from said cut.

7 3. A process for preparing a refined solution of a resin-formingunsaturated light oil hydrocarbon which is highly resistant to colorformation when subjected to conditions for the polymerization of saidunsaturated hydrocarbon which corn. prises subjecting light oil tofractional distillation to obtain a relatively close out of saidunsaturated hydrocarbon, treating said out with from 2% to 10% by volumeof sulfuric acid, said acid being from 60% to 80% in concentration andhaving added thereto a compound capable of furnishing manganese ion inthe resulting solution in quantity sufllcient to be "equivalent tobetween 0.1% and 5% 'by weight of potassium permanganate, said treatmenttaking place at a temperature between 10 C. and 30 C. but sufilcientlylow to avoid adding any appreciable permanent color to said hydrocarbondue to the strength of said acid, and then removing residual acid fromsaid out.

4. A process for preparing a refined styrene out which comprisessubjecting light oil to fractional distillation to obtain a cut thepreponder- 'ate part of which boils between 142 C. and

148 C., treating said cut with from 2% to 10% by volume of sulfuricacid, said acid being from 60% to 80% in concentration and having addedthereto a compound capable of furnishing manganese ion in the resultingsolution in quantity equivalent to between 0.1% and 5% by weight ofpotassium permanganate, said treatment takmg place at a temperaturebetween 10 C. and

30 C. but suiiiciently low to avoid adding any appreciable permanentcolor to said hydrocarbon due to the strength of said acid, and removingresidual acid from said styrene cut.

5. A process for preparing a refined methyl styrene out which comprisessubjecting light oil to fractional distillation to obtain a cut .thepreponderate part of which boils between 167 C.

and 175 C., treating said cut with from 2% to 10% by volume of sulfuricacid, said acid being from to 80% in concentration and having addedthereto a compound capable of furnishing manganese ion in the resultingsolution in quantity equivalent to between 0.1% to 5% by weight ofpotassium permanganate, said treatment tak ing place at a temperaturebetween -10 C. and 30 C. but sufiiciently low to avoid adding anyappreciable permanent color to said hydrocarbon due to the strength ofsaid acid, and removing residual acid from said methyl styrene cut.

6. A process for preparing a refined indene out which comprisessubjecting light oil to fractional distillation to obtain a cut thepreponderate part of which boils between 177 C. and 186 C., treatingsaid out with from 2% to 10% by volume of sulfuric acid, said acid beingfrom 60% to 80% in concentration and having added thereto a compoundcapable of furnishing manganese ion in the resulting solution inquantity v equivalent to between 0.1% to 5% by weight of potassiumpermanganate, said treatment taking place at a temperature between -10C. and

30 C. but sufficiently low to avoid adding any appreciable permanentcolor to said hydrocarbon due to the strength of said acid, and removingresidual acid from said indene cut.

7. In a process for the purification of a resinforming unsaturatedhydrocarbon derived from light oil, the steps of treating saidhydrocarbon in the liquid phase with sulfuric acid which is free fromany appreciable uncombined sulfur dioxide and sulfur trioxide and whichcontains a compound capable of furnishing an ioncontaining manganese inquantity equivalent to at least 0.1% of potassium permanganate, saidtreatment taking place at a temperature below C. and under conditionsincluding acid concentration and temperature sufficiently drastic toremove color forming vbodies but insufliciently drastic to polymerize alarge part of said resin-forming unsaturated hydrocarbon andinsufficiently drastic to add any appreciable permanent color to saidhydrocarbon, and removing said reagent from

